Semiconductor constructions, memory arrays, electronic systems, and methods of forming semiconductor constructions

ABSTRACT

The invention includes semiconductor constructions having trenched isolation regions. The trenches of the trenched isolation regions can include narrow bottom portions and upper wide portions over the bottom portions. Electrically insulative material can fill the upper wide portions while leaving voids within the narrow bottom portions. The trenched isolation regions can be incorporated into a memory array, and/or can be incorporated into an electronic system. The invention also includes methods of forming semiconductor constructions.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patentapplication Ser. No. 16/813,514, filed Mar. 9, 2020, which is adivisional application of U.S. patent application Ser. No. 16/200,593,now U.S. Pat. No. 10,622,442, filed Nov. 26, 2018, which is a divisionalapplication of U.S. patent application Ser. No. 15/895,882, filed Feb.13, 2018, now U.S. Pat. No. 10,170,545, which is a continuationapplication of U.S. patent application Ser. No. 15/385,783, filed Dec.20, 2016, now U.S. Pat. No. 9,929,233, which is a divisional applicationof U.S. patent application Ser. No. 14/480,454, filed Sep. 8, 2014, nowU.S. Pat. No. 9,559,163, which is a divisional application of U.S.patent application Ser. No. 12/835,042, filed Jul. 13, 2010, now U.S.Pat. No. 8,829,643, which is a divisional application of U.S. patentapplication Ser. No. 11/218,231, filed Sep. 1, 2005, now U.S. Pat. No.7,772,672, the disclosures of which are incorporated herein byreference.

TECHNICAL FIELD

The invention pertains to semiconductor constructions, memory arrays,electronic systems, and methods of forming semiconductor constructions.

BACKGROUND OF THE INVENTION

Trenched isolation regions (such as, for example, shallow trenchisolation regions) are commonly utilized in integrated circuitry forelectrically isolating electrical components from one another. Theisolation regions extend into a semiconductor substrate, and compriseinsulative material formed within trenches that have been etched intothe substrate.

High density plasma (HDP) oxide has been widely used in trenchedisolation regions. A problem that can occur during formation of trenchedisolation regions is that voids can become trapped in the trenchesduring deposition of the insulative material within the trenches. Thevoids will have dielectric properties different than that of theinsulative material, and accordingly will alter the insulativeproperties of the isolation regions. The voids can also cause issueswith further processing steps if the voids are exposed at any timeduring the processing steps. In response to these problems, numeroustechnologies have been developed for eliminating void formation withintrenched isolation regions.

It is becoming increasingly difficult to eliminate void formation withincreasing levels of integration (in other words, with the continuousshrinking of feature sizes with each new generation). Specifically,trenched isolation regions are becoming narrower and deeper with eachdevice generation, which renders it more difficult to uniformly fill thetrenched isolation regions with insulative material.

In light of the above-discussed difficulties, it would be desirable todevelop new methods for fabrication of trenched isolation regions whichalleviate problems associated with voids. Although the inventiondescribed herein was motivated, at least in part, by the desire toalleviate problems associated with void formation in trenched isolationregions, persons of ordinary skill in the art will understand uponreading this disclosure and the claims that follow that aspects of theinvention can have applications beyond trenched isolation regions.

SUMMARY OF THE INVENTION

In one aspect, the invention includes a semiconductor construction. Theconstruction comprises a semiconductor substrate having a trenchextending therein. A liner is along an interior of the trench andnarrows the trench. The liner comprises a thick bottom portion and athin upper portion over the bottom portion. The upper portion joins thebottom portion at a step. The lined trench has a wide upper portionjoining a constricted lower portion at said step. A substantially solidelectrically insulative material substantially fills the lined trench,and has a different composition from the liner.

In one aspect, the invention includes a memory array (such as, forexample, a FLASH memory array). The array comprises a plurality ofcharge storage cells supported by a semiconductor substrate, and aplurality of isolation regions extending within the substrate andproviding electrical isolation for the cells. At least some of theindividual isolation regions are contained within electricallyinsulative liners and comprise lower narrow portions joining to upperwide portions at steps. At least some of the individual isolationregions also comprise substantially solid insulative material within thenarrow portions and wide portions, and comprise voids substantiallyentirely contained within the narrow portions.

In one aspect, the invention includes an electronic system containing aprocessor and a memory device in data communication with the processor.At least one of the memory device and processor includes one or moreelectrical isolation regions contained within electrically insulativeliners and comprising lower narrow portions joining to upper wideportions at steps. The one or more electrical isolation regions containa non-gaseous material within the narrow portions and wide portions, andhave voids substantially entirely contained within the narrow portions.

In one aspect, the invention includes a method of forming asemiconductor construction. A semiconductor substrate is provided. Atrench is formed in the substrate, with the trench having a lower regionand an upper region over the lower region. A liner is formed within thetrench to narrow the trench. A sacrificial material is provided which isalong the liner within the lower region of the trench and not along theliner within the upper region of the trench. While the sacrificialmaterial is along the liner within the lower region of the trench, thethickness of the liner along the upper region of the trench is reduced.The sacrificial material is removed, and an electrically insulativematerial is formed within the trench and along the liner. Theelectrically insulative material substantially fills the upper region ofthe trench and leaves a void within the lower region of the trench.

In one aspect, the invention includes another method of forming asemiconductor construction. A semiconductor substrate is provided, and atrench is formed in the substrate. The trench is partially filled with afirst material to narrow the trench. The first material has a firstthickness. The thickness of the first material is reduced along an upperregion of the trench while the thickness of the first material along alower region of the trench remains at the first thickness. After thereduction of the thickness of the first material along the upper regionof the trench, the trench has a wide upper portion joining a constrictedlower portion at a step. Electrically insulative second material isformed within the narrowed trench. The electrically insulative secondmaterial substantially fills the wide upper portion and leaves a voidwithin the constricted lower portion.

In one aspect, the invention includes yet another method of forming asemiconductor construction. A semiconductor substrate is provided. Atrench is formed in the substrate. The trench has a lower region and anupper region over the lower region. A liner is formed within the trenchto narrow the trench. Non-oxidized silicon is provided to be along theliner within the lower region of the trench and not along the linerwithin the upper region of the trench. While the non-oxidized silicon isalong the liner within the lower region of the trench, the thickness ofthe liner is reduced along the upper region of the trench. Thenon-oxidized silicon is converted to silicon dioxide. After thethickness of the liner along the upper region of the trench is reduced,electrically insulative material is formed over the silicon dioxide tofill the upper region of the trench.

In one aspect, the invention includes yet another method of forming asemiconductor construction. A semiconductor substrate is provided. Apair of openings are formed to extend into the substrate. The individualopenings have upper regions and lower regions, and are spaced from oneanother by a pedestal of the substrate. Liners are formed within theopenings. Widths of the liners within the upper regions of the openingsare reduced relative to the widths of the liners within the lowerregions of the openings. After the widths of the liners are reduced,electrically insulative material is formed within the openings and alongthe liners. The electrically insulative material substantially fills theupper regions of the openings and leaves voids within the lower regionsof the openings. A transistor is formed which has a gate over thepedestal of the semiconductor substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, cross-sectional view of a semiconductor waferfragment shown at a preliminary processing stage of an exemplary aspectof the present invention.

FIG. 2 is a top view of a portion of a semiconductor constructioncomprising the cross-section of FIG. 1 along the line 1-1.

FIG. 3 is a view of the semiconductor wafer fragment of FIG. 1 shown ata processing stage subsequent to that of FIG. 1 .

FIG. 4 is a top view of a portion of a semiconductor constructioncomprising the cross-section of FIG. 3 along the line 3-3.

FIG. 5 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 3 .

FIG. 6 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 5 .

FIG. 7 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 6 .

FIG. 8 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 7 .

FIG. 9 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 8 .

FIG. 10 is a top view of a portion of a semiconductor constructioncomprising the cross-section of FIG. 9 along the line 9-9.

FIG. 11 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 9 .

FIG. 12 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 11 .

FIG. 13 is a view of a semiconductor construction comprising thecross-section of FIG. 12 along the line 12-12.

FIG. 14 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 3 in accordance with an aspect of theinvention alternative to that of FIG. 5 .

FIG. 15 is a view of the FIG. 14 wafer fragment shown at a processingstage subsequent to that of FIG. 14 .

FIG. 16 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 8 shown in accordance with an aspect ofthe invention alternative to that discussed above with reference to FIG.9 .

FIG. 17 is a view of the FIG. 16 wafer fragment shown at a processingstage subsequent to that of FIG. 16 .

FIG. 18 is a view of the FIG. 16 wafer fragment shown at a processingstage subsequent that of FIG. 17 .

FIG. 19 is a diagrammatic view of a computer illustrating an exemplaryapplication of the present invention.

FIG. 20 is a block diagram showing particular features of themotherboard of the FIG. 19 computer.

FIG. 21 is a high-level block diagram of an electronic system accordingto an exemplary aspect of the present invention.

FIG. 22 is a simplified block diagram of an exemplary memory deviceaccording to an aspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

High density plasma (HDP) oxide has been traditionally used for shallowtrench isolation (STI) fill due to the high oxide quality and good fillcapability. However, the HDP fill capability can be severely challengedas device feature sizes continue to shrink. At a 50 nanometer node, theSTI structure is typically only 50 nanometers wide and approximately3000 Å deep. It can be extremely difficult to fill an opening of suchhigh aspect ratio with HDP.

When HDP is utilized to fill openings having high aspect ratios, voidscan form within the openings. HDP is a simultaneous deposition and etchprocess, with silicon and oxygen atoms impinging on a surface to form asilicon dioxide film. Energetic particles can sputter from a surface ofthe film. This can keep openings from pinching off so that the bottomregions of the openings can be filled while avoiding trapping of voidswithin the openings. However, as gap widths become smaller and aspectratios become greater, another phenomena can become increasinglyproblematic: Specifically, atoms sputtered off of one side of an openingcan become redeposited on another side of the opening. This can cause anearly pinch-off of the openings before the bottom regions of theopenings are completely filled. Such results in void formation withinthe openings. Void formation at inappropriate locations can cause devicefunctionality issues, and also integration issues.

In some aspects of the present invention, openings are designed to forcevoids to occur at relatively low positions within the openings.Specifically, the openings are designed to have narrow portions at theirlowest-most regions, and wider portions above the narrow portions. Thenarrow portions can be created in STI trenches using an appropriatespacer, and sacrificial material (such as, for example, polycrystallinesilicon). In some aspects, the wide portions are subsequently filledwith an HDP fill process, and the wide portions can have appropriateaspect ratios to be easily uniformly filled by HDP-deposited oxide.

Exemplary aspects of the present invention are described below withreference to FIGS. 1-22 .

Referring initially to FIG. 1 , a semiconductor construction 10 isillustrated at a preliminary processing stage. The construction 10comprises a semiconductor substrate 12 having layers 17, 18 and 20thereover. Layer 18 can be an oxide-containing layer 18, layer 17 cancontaining silicon, and layer 20 can be a nitride-containing layer.Oxide-containing layer 18, can, for example, comprise, consistessentially of, or consist of silicon dioxide; layer 17 can comprise.consist essentially of, or consist of polycrystalline silicon (typicallyconductively-doped at the processing stage of FIG. 1 ), andnitride-containing layer 20 can, for example, comprise, consistessentially of, or consist of silicon nitride. Other layers can beutilized in addition to, or alternatively to, the layers 17, 18 and 20in various aspects of the invention (not shown).

Substrate 12 can comprise, consist essentially of, or consist of anyappropriate semiconductor material. In particular aspects, substrate 12can comprise bulk monocrystalline silicon lightly-doped with p-typedopant. To aid in interpretation of the claims that follow, the terms“semiconductive substrate” and “semiconductor substrate” are defined tomean any construction comprising semiconductive material, including, butnot limited to, bulk semiconductive materials such as a semiconductivewafer (either alone or in assemblies comprising other materialsthereon), and semiconductive material layers (either alone or inassemblies comprising other materials). The term “substrate” refers toany supporting structure, including, but not limited to, thesemiconductive substrates described above.

A patterned masking material 13 is over the layers 17, 18 and 20, andsuch defines a patterned mask. The masking material can be any suitablematerial, and in some aspects is photolithographically patternedphotoresist. The patterned mask is shown to comprise a pair of maskingblocks 14 and 16. Openings 22, 24 and 26 are between and beside themasking blocks, and extend to an uppermost surface of substrate 12.

FIG. 2 shows a top view of the construction 10. Such shows that themasking blocks 14 and 16 can be lines extending across a surface ofsubstrate 12, and that the openings 22, 24 and 26 can extendlongitudinally across the surface of layer 20.

Referring to FIGS. 3 and 4 , openings 22, 24 and 26 are extended throughlayers 17, 18 and 20, and into substrate 12 so that the openings nowbecome trenches extending into the substrate, and masking material 13(FIGS. 1 and 2 ) is removed. The extension of the openings through thelayers and into the substrate forms patterned lines 19 and 21 from thelayers 17, 18 and 20; and forms linear pedestals of the substrate 12beneath the patterned lines.

The openings can be extended through the layers and into the substratewith any suitable etch, or combination of etches, and to any suitabledepth. In some aspects, the openings will be extended into the substrateto a depth of at least about 1 micron.

The trenches 22, 24 and 26 terminate at bottom-most surfaces 23, 25 and27, respectively; and have substantially vertical sidewalls 31, 33 and35 extending upwardly from such bottom-most surfaces.

Referring to FIG. 5 , a material 40 is provided within trenches 22, 24and 26 to partially fill the trenches, and thus narrow the trenches.Material 40 can comprise any suitable composition or combination ofcompositions, and typically will be electrically insulative. Inexemplary aspects, material 40 can comprise, consist essentially of, orconsist of silicon dioxide. In other exemplary aspects, material 40 cancomprise multiple layers, as will be discussed in more detail below withreference to FIGS. 20 and 21 . If material 40 comprises a singlecomposition, the material can be substantially homogeneous. In aspectsin which material 40 comprises two or more layers, such layers can havedifferent compositions and/or other properties relative to one anotherso that one of layers can be selectively removed relative to another ofthe layers.

In the aspect of the invention of FIG. 5 , material 40 extends over andalong masking blocks 14 and 16, as well as extending within the trenches22, 24 and 26.

If material 40 comprises, consists essentially of, or consists ofsilicon dioxide, such material can be formed by appropriate depositionof silicon dioxide, such as, for example, deposition from tetraethylorthosilicate (TEOS). The material 40 can be formed to be conformalalong the surfaces 23, 25, 27, 31, 33 and 35, as shown. Another methodwhich can be used to form material 40 is thermal oxidation of exposedmaterials along surfaces 23, 25, 27, 31, 33 and 35. Such oxidation canform an entirety of the material 40 in some aspects, and in otheraspects can form only a portion of material 40. In aspects in which thethermally-grown layer is only a portion of material 40, another portionof material 40 can be deposited over the thermally-grown portion.

Material 40 can be formed to any suitable thickness, and in particularaspects can be formed to a thickness of from about 100 Å to about 200 Å.In some aspects, the material 40 can be formed to a thickness thatcovers about two-thirds of a total width of an individual trench in theshown cross-sectional view. In other words, the material 40 can beformed to a thickness such that the material fills about two-thirds ofthe total cross-sectional width of a trench (such as, for example, thetrench 24).

In some aspects of the invention, material 40 can be referred to as aliner, in that the material is lining the bottom-most surfaces andvertical surfaces of the trenches 22, 24 and 26.

Referring to FIG. 6 , a material 42 is formed over the liner 40 andwithin trenches 22, 24 and 26. In some aspects, liner 40 can be referredto as a first material, and material 42 can be referred to as a secondmaterial. In particular aspects, material 42 can ultimately be removedentirely from within the trenches 22, 24 and 26, and in such aspectsmaterial 42 can be referred to as a sacrificial material. If material 42is sacrificial, the material can be either electrically insulative orelectrically conductive.

Material 42 preferably has excellent fill properties so that thematerial uniformly fills the trenches 22, 24 and 26. An exemplarymaterial having suitable flow properties is polycrystalline silicon.Thus, material 42 can, in particular aspects, comprise, consistessentially of, or consist of silicon, and in some aspects can comprise,consist essentially of, or consist of polycrystalline silicon. Thesilicon can be either undoped (i.e., can have a dopant concentration ofless than or equal to about 10¹⁷ atoms/cm²) or can be doped with eitherp-type or n-type dopant. If liner 40 comprises silicon dioxide, it canbe advantageous for the silicon of material 42 to be either undoped orn-type doped, in that such can be easier to selectively remove relativeto silicon dioxide than is p-type doped silicon in a uniform andcontrolled fashion.

Referring to FIG. 7 , some of the material 42 is removed to leave thematerial only within the lower portions of the trenches 22, 24 and 26.In some aspects, the trenches can be considered to have lower regionsand upper regions over such lower regions. The locations of the lowerregions can be defined by the material 42 remaining at the processingstage of FIG. 7 , in that such material can be considered to fill thelower regions of the trenches while leaving the upper regions of thetrenches exposed. Thus, trenches 22, 24 and 26 can be considered tocomprise lower regions 44, 46 and 48 respectively, with such lowerregions being regions containing the remaining portions of material 42;and to comprise upper regions 54, 56 and 58 respectively, with suchupper regions being portions of the trenches above the remainingmaterial 42. If material 42 consists of polycrystalline silicon andliner 40 consists of silicon dioxide, the material 42 can be selectivelyetched relative to the liner with an NH₄F-based wet etch.

In particular aspects, the processing stage of FIG. 7 can be consideredto comprise material 42 provided to be along material 40 (oralternatively liner 40) within lower regions of the trenches, and to notbe along the material 40 within upper regions of the trenches. Theportion of material 40 against material 42 can be considered to be abottom portion of the material, and the portion of the material 40 thatis above material 42 can be considered to be an upper portion.

The material 42 remaining at the processing stage of FIG. 7 hasuppermost surfaces 43 at a depth 50 beneath the uppermost surfaces ofsubstrate 12. Ultimately, such depth will determine a depth to whichvoids present in isolation regions will be beneath gate oxide associatedwith transistor devices. It can be preferred that such depth be at least200 Å, and in particular aspects, such depth can be from about 200 Å toabout 1000 Å.

The shown uppermost surface 43 is in a concave shape, which can resultfrom some etching processes. It is to be understood that the uppermostsurface 43 can alternatively comprise numerous other configurations,including a flat shape or a convex shape.

Referring to FIG. 8 , material 42 protects liner 40 within lowermostregions of trenches 22, 24 and 26 while the liner in the uppermostregions of the trenches is exposed to an etch which reduces a thicknessof the liner. In the shown aspect, the reduction in the thickness of theliner does not entirely remove the liner from the uppermost regions ofthe trenches, but it is to be understood that the invention can alsoencompass aspects (not shown) in which the reduction of the thickness ofthe liner entirely removes the liner from the uppermost regions of thetrenches.

The liner remaining at the processing stage of FIG. 8 has a thick bottomportion within each of the trenches (with such bottom portions beinglabeled 60, 62 and 64 within the trenches 22, 24 and 26, respectively);and has thin upper portions over such bottom portions (with the thinupper portions being labeled 70, 72 and 74 within the trenches 22, 24and 26, respectively). The thin upper portions join the thick bottomportions at steps (with the steps being labeled 63, 65 and 67 in thetrenches 22, 24 and 26, respectively). In some aspects, the liner withinthe lower portions can be considered to comprise substantially verticalsidewalls, and the steps 63, 65 and 67 can extend substantiallyperpendicularly to such sidewalls. In other aspects, such as the shownaspect, the steps can extend non-perpendicularly to the such sidewalls.It can be advantageous that the steps be relatively abrupt, in that thetransition between the wide lower portions of the liners and the narrowupper portions of the liners ultimately defines void-trapping regions insome aspects of the invention.

The thicknesses of the upper portions 70, 72 and 74 of the liner 40 can,in some aspects, be reduced to a final thickness of from about 10 Å toabout 100 Å, with the typical final thickness being about 30 Å. In someaspects of the invention, the reduction in thickness of the upperportions of the liner reduces the thickness of the upper portions of theliner from a first thickness to a second thickness which is from about10% to about 50% of the first thickness.

Referring to FIGS. 9 and 10 , material 42 (FIG. 8 ) is removed with anetch which is selective for material 42 relative to liner 40. Forpurposes of interpreting this disclosure and the claims that follow, anetch is considered to be selective for one material relative to anotherif the etch removes said one material at a faster rate than said othermaterial, which can include, but is not limited to, etches which are100% selective for one material relative to another. In aspects in whichliner 40 comprises silicon dioxide and sacrificial material 42 comprisesnon-oxidized silicon, the etch utilized to remove material 42 can be aNH₄F-based wet etch.

The construction of FIGS. 9 and 10 comprises trenches 22, 24 and 26having wide upper portions 80, 82 and 86 joined to constricted lowerportions 90, 92 and 96. Thus, the liners 40 have changed the internalshapes of the trenches from the initial shape at the processing stage ofFIG. 1 having substantially vertical sidewalls to a new shape havingconstricted lower portions joining to wide upper portions.

As discussed previously, liner 40 can be homogeneous, and accordinglythe liner can have the same composition at the upper portions 70, 72 and74 above the steps, as at the lower portions 60, 62 and 64 beneath thesteps. In other aspects (discussed below with reference to FIGS. 14 and15 ) the liner can comprise multiple layers, and one of the layers canbe substantially removed from the upper portions of the liners at theprocessing stage of FIG. 9 while remaining in the lower portions of theliners so that the lower (or bottom) portions of the liners comprise adifferent composition than the upper portions of the liners.

Referring to FIG. 11 , a material 100 is provided within trenches 22, 24and 26. The material 100 can be an electrically insulative material, andin particular aspects can comprise, consist essentially of, or consistof silicon dioxide. For instance, material 100 can be HDP-depositedsilicon dioxide.

The widened upper portions 80, 82 and 86 of trenches 22, 24 and 26 haveappropriate widths and aspect ratios so that the material 100 uniformlyfills such widened upper portions. In contrast, the narrow lowerportions 90, 92 and 96 of the trenches are too narrow for the material100 to uniformly fill them, and so voids 102 are formed within the lowerportions. The abrupt transition between the lower portions and upperportions accomplished with the steps 63, 65 and 67 enables the voids tobe controllably formed to be retained within the narrow portions.

The trench 24 is shown having a width 106 of the wide portion 82 and awidth 108 of the narrow portion 92. In particular aspects, the width 106will be greater than or equal to about 60 nanometers and the width 108will be less than or equal to about 30 nanometers. In some aspects, thewidth 108 will be less than or equal to about 70% of the width 106, andin typical aspects will be from about 20% to about 70% of the width 106.In other words, the trench 24 in the shown cross-sectional view willhave a constricted lower portion that is typically from about 20% toabout 70% as wide as an upper wide portion.

The material 100 can, in some aspects, be referred to as a“substantially solid” material. Such indicates that the material 100 canbe, but is not limited to, pure solids, and accordingly can comprisegelatinous materials and other semi-solid materials, including, forexample, various glasses. The material 100 can comprise any suitablecomposition or combination of compositions, and although it is shown tobe substantially homogeneous, can comprise multiple layers. Inparticular aspects, material 100 is an electrically insulative materialsuitable for trenched isolation regions, and in such aspects can, forexample, comprise, consist essentially of, or consist of silicon dioxide

The narrow portions 90, 92 and 96 of the trenches define locations wherevoids 102 are formed within the trenches. Specifically, the voids willbe substantially entirely retained within the narrow portions, with theterm “substantially entirely retained within the narrow portions”meaning that the vast majority of the volume of a void is retainedwithin a narrow portion. More specifically, such phrase means that atleast about 75% of the volume of a void is retained within a narrowportion. In some aspects, the entirety of a void will be retained withinthe narrow portion of an trench. In other words, the entirety of thevoid will be at or below the elevational level of the steps which jointhe narrow portion to the wide portion (for example, the steps 63, 65and 67 of FIG. 11 ).

Utilization of appropriate steps can provide clear delineation betweenthe wide portions of the trenches and the narrow portions of thetrenches, which can assist in forcing the voids to be retainedsubstantially entirely within the narrow portions. In contrast,utilization of steps having a very gradual slope between the narrowportion of a trench and the wide portion of the trench can createdifficulty in controlling the location of voids within the trenches. Itis to be understood, however, that any steps can be used which aresuitable for delineating the narrow portions relative to the wideportions so that voids can be controllably retained within theparticular regions of the trenches. Further, although the shown stepsare only single steps between the wide portions of the openings and thenarrow portions, it is to be understood that the invention alsoencompasses aspects in which multiple steps are provided between thewidest portion of an opening and the narrowest portion of an opening. Insuch aspects, the opening can still be considered to have “a” stepbetween the wide portion and the narrow portion, but such step will beone of a plurality of steps between the wide portion and the narrowportion.

Voids 102 can contain any material which differs from the material 100.Thus, the term “void” is utilized to refer to regions devoid of material100, but not necessarily devoid of other matter. The difference betweenthe material of the voids and the material 100 can be, for example,differences in one or more of phase, density, and chemical composition.In some aspects of the invention, the voids 102 can be gaseous regions,and material 100 can be a non-gaseous material. If material 100 sealsthe voids from the atmosphere exterior of material 100, the particulargas within the voids can be the ambient present during deposition ofmaterial 100, and/or gases formed by out-gassing from material 100during deposition of the material 100.

In some aspects, material 100 can comprise substantially the samecomposition as liner 40. For instance, liner 40 can consist essentiallyof, or consist of silicon dioxide, and material 100 can also consistessentially of or consist of silicon dioxide. In other aspects, liner 40can comprise a different composition and/or density than material 100.For instance, in some aspects at least a portion of liner 40 can consistessentially of, or consist of silicon nitride, while material 100consists essentially of, or consists of silicon dioxide.

Referring to FIG. 12 , construction 10 is subjected to planarization toform a planarized upper surface 111. The planarized upper surfaceextends across the material 100 within trenches 22, 24 and 26, as wellas across regions between the trenches.

FIG. 13 is a top view of the construction 10 at the processing stage ofFIG. 12 .

In some aspects, materials 40 and 100 are electrically insulative, andform trenched isolation regions within the trenches 22, 24 and 26. Insuch aspects, the voids 102 can also be considered to be part of thetrenched isolation regions. It can be advantageous to incorporate voidsinto trenched isolation regions in that the voids will typically havevery low dielectric constants, which can be desired for someapplications of trenched isolation regions.

The trenched isolation regions within trenches 22, 24 and 26 can bereferred to as first, second and third trenched isolation regionsrespectively. Any suitable circuitry can be formed proximate thetrenched isolation regions to incorporate the trenched isolation regionsinto an integrated circuit construction. For instance, thesilicon-containing material 17 can be utilized as gate material oftransistors, with source/drain regions of the transistors being formedout of the plane of the cross-section of FIG. 12 . The trenchedisolation regions can be utilized to electrically isolate thetransistors from one another. In particular aspects, such transistorscan be incorporated into FLASH devices. The FLASH devices can befabricated as conventional devices, utilizing methodologies known topersons of ordinary skill in the art.

The aspects of the invention discussed above are exemplary aspects, andit is to be understood that the invention encompasses other embodiments.For instance, FIG. 14 shows construction 10 at a processing stagesubsequent to that of FIG. 4 and alternative to that shown in FIG. 5 .Identical numbering will be used in referring to FIG. 14 as was utilizedabove in describing FIG. 5 , where appropriate.

The construction of FIG. 14 comprises the substrate 12 having trenches22, 24 and 26 extending therein, and comprises the liner 40 extendingwithin the trenches. However, in contrast to the embodiment of FIG. 5 ,the liner 40 of FIG. 14 is shown to comprise two separate layers 300 and302. The layers can differ in composition and/or density relative to oneanother, and specifically layer 302 can be selectively etchable relativeto layer 300. In particular aspects, layer 302 can comprise, consistessentially of, or consist of silicon dioxide, and layer 300 cancomprise, consist essentially of, or consist of silicon nitride.Although liner 40 is shown to comprise two layers in the aspect of FIG.14 , it is to be understood that the liner can comprise more than twolayers in other aspects of the invention. Also, it is to be understoodthat the relative thicknesses of the layers utilized in material 40 canbe any relative thicknesses suitable for particular applications. Thus,the shown aspect in which layer 302 is thicker than layer 300 is but oneexemplary aspect, and the invention includes other aspects in whichlayer 300 is thicker, or in which layers 300 and 302 are about the samethickness as one another.

Referring next to FIG. 15 , the construction of FIG. 14 is shown at aprocessing stage analogous to that discussed previously with referenceto FIG. 8 . Specifically, a sacrificial material 42 is formed withinlower portions of the trenches 22, 24 and 26, and subsequently layer 40is subjected to etching conditions which remove the portions of layer 40that are not protected by material 42. In the shown aspect of theinvention, such removal selectively removes layer 302 of material 40,but does not remove layer 300. Accordingly, layer 300 can function as anetch stop during the thinning of material 40, which can enablerelatively stringent control of the final thickness of material 40within the regions that have been thinned.

The construction 10 of FIG. 15 is shown to comprise regions 310 whereetching has penetrated past an uppermost surface of sacrificial material42 to form recesses along the material. In other words, some of theliner 40 along the sacrificial material has been reduced in thicknessduring the reduction in thickness of the liner which was not protectedat all by the sacrificial material. In some aspects of the invention,the formation of recesses 310 can be considered to be an over-etch ofthe material 40 to extend the reduction in thickness of material 40along some of the sacrificial material 42. Such over-etch can occurregardless of whether the liner 40 comprises multiple layers as shown inFIGS. 14 and 15 , or comprises a single layer as shown in FIGS. 5-8 .The over-etch can be desired in some aspects of the invention to alterthe elevational boundary between the widened portions of material 40 andthe narrowed portions of material 40 relative to where the boundarieswould exist without such over-etch, and/or to change the shape of stepsoccurring at the interfaces of wide upper portions of the lined trenchesand narrow lower portions of the lined trenches (in other words, stepsanalogous to the steps 63, 65 and 67 described previously).

FIG. 16 shows yet another aspect of the present invention. FIG. 16 showsconstruction 10 at a processing stage subsequent to that of FIG. 8 inaccordance with an aspect of the invention alternative to that of FIG. 9. In referring to FIG. 16 , identical numbering will be used as wasutilized above in describing the embodiment of FIGS. 1-13 , whereappropriate.

The construction of FIG. 16 is identical to that of FIG. 8 , except thatthe material 42 of FIG. 8 has been converted to a composition 350. Inparticular aspects of the invention, material 42 of FIG. 8 cancorrespond to non-oxidized silicon (such as, for example,polycrystalline silicon and/or amorphous silicon), and composition 350of FIG. 16 can correspond to oxidized silicon (specifically silicondioxide). Composition 350 can be formed from the non-oxidized silicon bysubjecting such silicon to thermal oxidation. The oxidized silicon 350fills lowermost regions of trenches 22, 24 and 26, and is anelectrically insulative material suitable for incorporation intotrenched isolation regions.

Referring next to FIG. 17 , electrically insulative material 100 isformed to fill the wide portions of trenches 22, 24 and 26.

In subsequent processing, the construction of FIG. 17 can be subjectedto planarization to form the structure shown in FIG. 18 . Such structurecomprises trenched isolation regions containing insulative material 100in combination with insulative material 350.

The processing discussed above with reference to FIGS. 1-18 is exemplaryprocessing, and it is to be understood that the invention can includevarious modifications and alternative embodiments to the embodimentsspecifically described in FIGS. 1-18 .

FIG. 19 illustrates generally, by way of example but not by way oflimitation, an embodiment of a computer system 400 according to anaspect of the present invention. Computer system 400 includes a monitor401 or other communication output device, a keyboard 402 or othercommunication input device, and a motherboard 404. Motherboard 404 cancarry a microprocessor 406 or other data processing unit, and at leastone memory device 408. Memory device 408 can comprise various aspects ofthe invention described above. Memory device 408 can comprise an arrayof memory cells, and such array can be coupled with addressing circuitryfor accessing individual memory cells in the array. Further, the memorycell array can be coupled to a read circuit for reading data from thememory cells. The addressing and read circuitry can be utilized forconveying information between memory device 408 and processor 406. Suchis illustrated in the block diagram of the motherboard 404 shown in FIG.20 . In such block diagram, the addressing circuitry is illustrated as410 and the read circuitry is illustrated as 412. Various components ofcomputer system 400, including processor 406, can comprise one or moreof the memory constructions described previously in this disclosure.

Processor device 406 can correspond to a processor module, andassociated memory utilized with the module can comprise teachings of thepresent invention.

Memory device 408 can correspond to a memory module. For example, singlein-line memory modules (SIMMs) and dual in-line memory modules (DIMMs)may be used in the implementation which utilize the teachings of thepresent invention. The memory device can be incorporated into any of avariety of designs which provide different methods of reading from andwriting to memory cells of the device. One such method is the page modeoperation. Page mode operations in a DRAM are defined by the method ofaccessing a row of a memory cell arrays and randomly accessing differentcolumns of the array. Data stored at the row and column intersection canbe read and output while that column is accessed.

An alternate type of device is the extended data output (EDO) memorywhich allows data stored at a memory array address to be available asoutput after the addressed column has been closed. This memory canincrease some communication speeds by allowing shorter access signalswithout reducing the time in which memory output data is available on amemory bus. Other alternative types of devices include SDRAM, DDR SDRAM,SLDRAM, VRAM and Direct RDRAM, as well as others such as SRAM or FLASHmemories.

Memory device 408 can comprise memory formed in accordance with one ormore aspects of the present invention.

FIG. 21 illustrates a simplified block diagram of a high-levelorganization of various embodiments of an exemplary electronic system700 of the present invention. System 700 can correspond to, for example,a computer system, a process control system, or any other system thatemploys a processor and associated memory. Electronic system 700 hasfunctional elements, including a processor or arithmetic/logic unit(ALU) 702, a control unit 704, a memory device unit 706 and aninput/output (I/O) device 708. Generally, electronic system 700 willhave a native set of instructions that specify operations to beperformed on data by the processor 702 and other interactions betweenthe processor 702, the memory device unit 706 and the I/O devices 708.The control unit 704 coordinates all operations of the processor 702,the memory device 706 and the I/O devices 708 by continuously cyclingthrough a set of operations that cause instructions to be fetched fromthe memory device 706 and executed. In various embodiments, the memorydevice 706 includes, but is not limited to, random access memory (RAM)devices, read-only memory (ROM) devices, and peripheral devices such asa floppy disk drive and a compact disk CD-ROM drive. One of ordinaryskill in the art will understand, upon reading and comprehending thisdisclosure, that any of the illustrated electrical components arecapable of being fabricated to include memory constructions inaccordance with various aspects of the present invention.

FIG. 22 is a simplified block diagram of a high-level organization ofvarious embodiments of an exemplary electronic system 800. The system800 includes a memory device 802 that has an array of memory cells 804,address decoder 806, row access circuitry 808, column access circuitry810, read/write control circuitry 812 for controlling operations, andinput/output circuitry 814. The memory device 802 further includes powercircuitry 816, and sensors 820, such as current sensors for determiningwhether a memory cell is in a low-threshold conducting state or in ahigh-threshold non-conducting state. The illustrated power circuitry 816includes power supply circuitry 880, circuitry 882 for providing areference voltage, circuitry 884 for providing the first wordline withpulses, circuitry 886 for providing the second wordline with pulses, andcircuitry 888 for providing the bitline with pulses. The system 800 alsoincludes a processor 822, or memory controller for memory accessing.

The memory device 802 receives control signals from the processor 822over wiring or metallization lines. The memory device 802 is used tostore data which is accessed via I/O lines. It will be appreciated bythose skilled in the art that additional circuitry and control signalscan be provided, and that the memory device 802 has been simplified tohelp focus on the invention. At least one of the processor 822 or memorydevice 802 can include a memory construction of the type describedpreviously in this disclosure.

The isolation structures described herein can be particularly useful forincorporation in to FLASH memory, and in such aspects the FLASH can beutilized in removable memory cards and other removable memory devices.Such removable memory devices can be used for storing or transferringdata for numerous electronic systems, including, for example, cameras,phones, computers, etc.

The various illustrated systems of this disclosure are intended toprovide a general understanding of various applications for thecircuitry and structures of the present invention, and are not intendedto serve as a complete description of all the elements and features ofan electronic system using memory cells in accordance with aspects ofthe present invention. One of the ordinary skill in the art willunderstand that the various electronic systems can be fabricated insingle-package processing units, or even on a single semiconductor chip,in order to reduce the communication time between the processor and thememory device(s).

Applications for memory cells can include electronic systems for use inmemory modules, device drivers, power modules, communication modems,processor modules, and application-specific modules, and may includemultilayer, multichip modules. Such circuitry can further be asubcomponent of a variety of electronic systems, such as a clock, atelevision, a cell phone, a personal computer, an automobile, anindustrial control system, an aircraft, and others.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

The invention claimed is:
 1. A method of forming a semiconductorconstruction, comprising: providing a semiconductor substrate; forming atrench in the substrate; partially filling the trench with a firstmaterial to narrow the trench, the first material having a firstthickness; reducing the thickness of the first material along an upperregion of the trench while the thickness of the first material along alower region of the trench remains at the first thickness; after saidreducing of the thickness, the narrowed trench having a wide upperportion joining a constricted lower portion at a step, the step curveddownwardly; and forming electrically insulative second material withinthe narrowed trench, the electrically insulative second materialsubstantially filling the wide upper portion and leaving a void withinthe constricted lower portion.
 2. The method of claim 1 wherein thefirst material consists essentially of silicon dioxide.
 3. The method ofclaim 1 wherein the first material is substantially homogeneous.
 4. Themethod of claim 1 wherein the first material comprises at least twolayers having different compositions relative to one another, andwherein the reduction of the thickness of the first material along theupper region of the trench comprises removal of one of the layersselectively relative to at least one other of the layers.
 5. The methodof claim 1 wherein: the semiconductor substrate comprises patternedlines over a semiconductor material; the trench is between a pair of thepatterned lines and extends into the semiconductor material; and thefirst material is formed to extend over and along the lines as well aswithin the trench.
 6. The method of claim 5 wherein the patterned linescomprise a silicon-nitride-containing layer over asilicon-dioxide-containing layer.
 7. A method of forming a semiconductorconstruction, comprising: providing a semiconductor substrate; forming atrench in the substrate, the trench having a lower region and an upperregion over the lower region; forming a liner within the trench tonarrow the trench; providing non-oxidized silicon to be along the linerwithin the lower region of the trench and not along the liner within theupper region of the trench; while the non-oxidized silicon is along theliner within the lower region of the trench, reducing the thickness ofthe liner along the upper region of the trench; converting thenon-oxidized silicon to silicon dioxide; and after reducing thethickness of the liner along the upper region of the trench, formingelectrically insulative material over the silicon dioxide to fill theupper region of the trench.
 8. The method of claim 7 wherein the lineris substantially homogeneous.
 9. The method of claim 7 wherein the linercomprises at least two layers having different compositions relative toone another, and wherein the reduction of the thickness of the linerwithin the upper region of the trench comprises removal of one of thelayers selectively relative to at least one other of the layers.
 10. Themethod of claim 7 wherein some of the liner along the non-oxidizesilicon is also reduced in thickness during the reduction of thethickness of the liner within the upper region of the trench.
 11. Themethod of claim 7 wherein the non-oxidized silicon consists ofpolycrystalline silicon.
 12. A method of forming a semiconductorconstruction, comprising: providing a semiconductor substrate; forming atrench in the substrate; partially filling the trench with a firstmaterial to narrow the trench, the first material having a firstthickness; reducing the thickness of the first material along an upperregion of the trench while the thickness of the first material along alower region of the trench remains at the first thickness; after saidreducing of the thickness, the narrowed trench having a wide upperportion joining a constricted lower portion at a step; formingelectrically insulative second material within the narrowed trench, theelectrically insulative second material substantially filling the wideupper portion and leaving a void within the constricted lower portion;and wherein the first material comprises at least two layers havingdifferent compositions relative to one another, and wherein thereduction of the thickness of the first material along the upper regionof the trench comprises removal of one of the layers selectivelyrelative to at least one other of the layers.